Ata' al-Khurasani (may Allah have mercy on him) said: A man came to Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) and said: I married a woman on the condition that separation and intercourse would be in her hands. He said: You have gone against the Sunnah and handed the matter to someone not entitled to it; the dowry, separation and intercourse are in your hands. Another man came to him and said: I married a woman and stipulated to her that if I do not bring such-and-such by such-and-such a time, I have no marriage. Ibn Abbas (may Allah be pleased with them both) said: The marriage is valid, but the condition counts for nothing.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14442